Vegetable caterpillar

Caterpillar fungus (Cordyceps sinensis) is a species of parasitic fungus that is found in south-western mountainous China and that attacks and grows on caterpillars, specifically on larvae from the genus Thitarodes. A caterpillar killed by a C. sinensis fungus growing on it is also called "vegetable caterpillar" even though no plant matter is involved. It is known in the West primarily from its use in Traditional Chinese medicine, where it is a prized ingredient.

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Names

In Tibetan it is known as Yartsa Gunbu [Wylie: dbyar rtswa dgun 'bu], source of Nepali:यार्सागुम्बा, Yarshagumba, Yarchagumba. It is also known as "keera jhar" in India. Its name in Chinese "dong chong xia cao" (冬虫夏草) means "winter worm, summer grass" (meaning "worm in the winter, (turns to) plant in the summer"). The Chinese name is a literal translation of the original Tibetan name, which was first recorded in the 15th Century by the Tibetan doctor Zurkhar Namnyi Dorje (Wylie: Zur mkhar mnyam nyid rdo rje’s [1439-1475]) in his text: Man ngag bye ba ring bsrel (Oral Instructions on a Myriad of Medicines).

In traditional Chinese medicine, its name is often abbreviated as "chong cao", a name that also applies to other Cordyceps species, such as C. militaris.

It is also known as Aweto in China and Tibet, and as Yarchagumba in Tibet. It is sometimes known as tochukaso/tohchukaso.

Natural history

The caterpillar prone to infection by the fungus lives underground in alpine grass and shrublands on the Tibetan Plateau and the Himalayas at an altitude between 3000m and 5000m. Spending up to five years underground before pupating, the caterpillar is attacked while feeding on roots. The fungus invades the body of the Thitarodes caterpillars, filling its entire body cavity with mycelium and eventually killing and mummifying it. The caterpillars die near the tops of their burrows. The dark brown to black fruiting body (or mushroom) emerges from the ground in spring or early summer, always growing out of the forehead of the caterpillar. The long, usually columnar fruiting body reaches 5-15 cm above the surface and releases spores.

In Nepal caterpillar fungus is found on the subalpine pastures in Dolpo in Karnali Zone. It is also common in Bhutan and India's Himachal Pradesh. Reports from distribution outside of High Asia are erroneous and relate to other species of Cordyceps, i.e. Cordyceps militaris.

It is not certain how the fungus infects the caterpillar, possibly by ingesting a fungal spore or by the fungus mycelium invading the insect through one of its breathing pores. Also, the larvae could have a symbiotic relationship with the fungus.

Use in Chinese medicine

First mentioning of Cordyceps sinensis in Traditional Chinese Medicine was in the 18th Century [In: Wu Yiluo’s “Ben cao cong xin” - “New compilation of materia medica” in 1757].

The entire fungus-caterpillar combination is hand-collected for medicinal use.

The fungus is highly prized by practitioners of Tibetan medicine, Chinese medicine and traditional herbal Folk medicines, in which it is used as an aphrodisiac and as a treatment for a variety of ailments, from fatigue to cancer. It is regarded as having an excellent balance of yin and yang (through being apparently both animal and vegetable), though it is in actuality not vegetable, but fungal. Assays have found that Cordyceps species produce many pharmacologically active substances. They are now cultivated on an industrial scale for their medicinal value.

The popularity of this fungus recently grew because two female Chinese athletes, Wang Junxia and Qu Yunxia, who beat the world records for 1500, 3000 and 10000 meters in the early 1990s, used it at the recommendation of their coach; the coach said that this fungus, which has been known for 2000 years, helps athletes.

According to Bensky (2006), laboratory-grown C. sinensis mycelium has similar clinical efficacy and less associated toxicity. He notes a toxicity case of constipation, abdominal distension, and decreased peristalsis, two cases of irregular menstruation, and one case report of amenorrhea following ingestion of tablets or capsules containing C. sinensis. In Chinese medicine C. sinensis is considered sweet and warm, it enters the Lung and Kidney channels, and the typical dosage is 3-9 grams (Bensky 2006).

Economics and impact

Its value gave it a role in the Nepalese Civil War, as the Nepalese Maoists and government forces fought for control of the lucrative export trade during the June - July harvest season. Collecting yarchagumba in Nepal had only been legalised in 2001, and now demand is highest in countries such as China, Thailand, Korea and Japan. By 2002, the herb was valued at R 105,000 ($1,435) per kilogram, allowing the government to charge a royalty of R 20,000 ($280) per kilogram.

In Tibet, Yartsa Gunbu developed to the most important source of cash income in rural Tibet. Prices are increasing continuously, especially since the late 1990s. One kg trades in 2007 for US$3000 (lowest quality) to over US$15,000 (best quality = big larvae).

The search for Cordyceps sinensis, is often preceived to pose a threat for the Tibetan Plateau where it grows. However, it has been collected for centuries and is still common in such collection areas. Still, current collection rates are much higher than in historical times.

The high price of wild C. sinensis has led unscrupulous harvesters to insert twigs or even lead wires into the stromata, thereby increasing the weight and price paid. Cultivated C. sinensis mycelium is a more sustainable alternative to wild-harvested C. sinensis, and may offer improved consistency. Artificial culture of C. sinensis is typically by growth of the pure mycelium in liquid culture--stromata are not produced apart from the insect host.

References

• D Bensky, A Gamble, S Clavey, E Stoger, L Lai Bensky. 2006. Chinese Herbal Medicine Materia Medica (3rd ed.). Eastland Press.

See also

• Cordyceps